The feature size of a large scale integrated circuit is directly determined by a photolithography process, which is one of the key processes in large scale integrated circuit manufacturing. A lithography machine is one of the most important apparatuses in the photolithography process. A projection objective system, an alignment system and a super-precise workpiece stage system are three core technologies in the lithography machine. Wherein, the super-precise workpiece stage system comprises a reticle stage system for supporting mask plates and a silicon wafer stage system for supporting silicon wafers.
The reticle stage system consists of a movable platform of the reticle stage, a balance mass, a drive motor for the movable platform, a mask plate, a base, a vibration isolation system, a measurement system and the like. The exposure process of the lithography machine requires that the drive motor drives the movable platform carrying the mask plate to move to and fro in an “acceleration—uniform velocity—deceleration” movement in a large stroke (>132 mm) along a scanning direction, and to move in a fine motion (±2 mm) with other degrees of freedom. Based on the structures of the movable platforms of the reticle stages, the reticle stages may be divided into two types, i.e., a reticle stage with a movable platform utilizing a coarse motion and fine motion laminated structure, and a reticle stage with a movable platform utilizing a coarse motion and fine motion integrated structure. As for the reticle stage utilizing the coarse motion and fine motion laminated structure, the movable platform of the reticle stage consists of a coarse movable platform which can achieve large stroke movement, and a micropositioner which can achieve high precision fine adjustment. As for the reticle stage utilizing the coarse motion and fine motion integrated structure, the large stroke movement and the high precision fine adjustment are achieved by an individual movable platform of a coarse motion and fine motion integrated reticle stage.
The movable platform utilizing the coarse motion and fine motion integrated structure has features of lighter mass, less cable perturbation and the like, and advantages of less power consumption during the operation of the reticle stage, lower requirement on thrusts of the motors and more accurate theoretical model, some scholars have carried out research on it. In prior art, the six degrees of freedom movement of the movable platform of the coarse motion and fine motion integrated reticle stage is achieved by linear motors, and each of the linear motors may provide a thrust in the movement direction of the mover of the motor and a thrust in a direction perpendicular to the movement direction of the mover of the motor. In order to control the leveling movement and focusing movement of the movable platform of the coarse motion and fine motion integrated reticle stage, at least three linear motors are required to provide the thrusts in the vertical direction. In order to control the six degrees of freedom movement of the movable platform of the coarse motion and fine motion integrated reticle stage, at least another two linear motors are required, which provide thrusts in a different direction from that of the aforementioned linear motors. Due to structural restrictions, the two kinds of motors are different in structure, which increases the design complexity of the drive motors for the movable platform of the coarse motion and fine motion integrated reticle stage. The two kinds of linear motors with different structures are arranged on the movable platform of the coarse motion and fine motion integrated reticle stage in parallel, so that the width of the movable platform of the coarse motion and fine motion integrated reticle stage is increased, and the natural frequency and the control bandwidth of the movable platform of the coarse motion and fine motion integrated reticle stage are reduced, thereby influencing the control precision.